The purposed of the proposed research is to molecularly clone and characterize a recently discovered Feline lentivirus (termed FTLV) which appears to cause a syndrome very similar to the human immunodeficiency virus (HIVS). FTLV is particularly important in that it offers an excellent model system for the development of a lentivirus vaccine and for detailed studies of the etiology of a T-lymphotropic virus in its primary host organism. The overall objective is to develop FTLV as a model for a vaccine to lentivirus infections. Since this virus has only recently been identified, considerable groundwork will first be required before proceeding to more detailed studies. The specific aims of this proposal are to 1) obtain an infectious molecular clone of FTLV; 2) obtain the nucleotide sequence of the virus; 3) define the gene products encoded by FTLV, using antisera to synthetic peptides to detect proteins predicted from the nucleic acid sequence; 4) define epitopes that serve as targets for virus neutralization, using both antisynthetic peptide antibodies directed to peptides corresponding to regions of the envelope gene as well as monoclonal antibodies made against native envelope proteins; 5) test the efficacy of synthetic peptides identified in (3) for in vivo protection form FTLV infection; and 6) characterize the glycosylation patterns of FTLV and assess the influences of carbohydrate on immune surveillance of the virus. The results of the above studies will contribute to our understanding of the molecule biology of the T-lymphotropic lentiviruses and should be directly applicable to the development of a vaccine against HIV.